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Rapid serial enzyme measurements in evaluation of patients with suspected myocardial infarction
D R Dufour1, A LaGrenade, J Guerra
1Laboratory Service, Veterans Administration Medical Center, Washington, DC 20422.
Insights
Serial enzyme measurements, including creatine kinase (CK), can help diagnose acute myocardial infarction (AMI) early. This approach improves diagnostic accuracy and may reduce unnecessary hospital admissions for suspected heart attacks.
Area of Science:
- Cardiology
- Clinical Biochemistry
Background:
- Accurate diagnosis of acute myocardial infarction (AMI) is challenging at initial presentation.
- Current clinical and laboratory criteria often fail to confirm AMI in admitted patients.
Purpose of the Study:
- To evaluate the effectiveness of serial enzyme measurements in diagnosing AMI.
- To assess the utility of enzyme changes in patients presenting with acute cardiac symptoms.
Main Methods:
- Retrospective analysis of 1,214 patients with acute cardiac symptoms (<24 hours duration).
- Evaluation of serial creatine kinase (CK) levels and CK to aspartate aminotransferase ratios.
- Analysis of enzyme changes at presentation and 8 hours later.
Main Results:
- A positive delta-CK identified AMI in 98% of patients with initially normal CK.
- A low CK to aspartate aminotransferase ratio identified AMI in 98% of patients with elevated total CK.
- Both enzyme ratios demonstrated >90% sensitivity for AMI detection.
Conclusions:
- Serial enzyme measurements are valuable for diagnosing suspected AMI.
- This diagnostic approach can potentially decrease the number of non-AMI patients admitted to coronary care units.
Abstract:
Because clinical and laboratory criteria cannot accurately establish the presence or absence of acute myocardial infarction (AMI) at the time of initial presentation, this diagnosis is not confirmed in the majority of patients admitted to coronary care units. To study the effectiveness of serial changes in enzyme activity in specimens taken at presentation and 8 hours later in establishing the likelihood of AMI, the results in 1,214 patients with acute cardiac symptoms of less than 24 hours' duration were retrospectively evaluated. In 1,007 patients with initially normal creatine kinase (CK), an increase in CK (positive delta-CK) occurred in 98% of patients with AMI and 16% of patients without AMI. In 196 patients with elevated total CK, a low ratio of CK to aspartate aminotransferase was found in 98% of patients with AMI and 33% of patients without AMI. These 2 enzyme ratios had a sensitivity greater than 90% in patients with typical and atypical histories. The overall predictive value of serial enzyme measurements for AMI was 53%, compared with 18% in patients selected for admission. These results suggest that serial enzyme measurements could be used in the initial evaluation of patients with suspected AMI, and have the potential to reduce the number of patients admitted to coronary care units who do not have AMI.